Process for manufacturing insulating material

ABSTRACT

Process for producing cellulose-based thermal and/or acoustic insulation material, characterised in that said insulation material comprises paper sludge and wherein said insulation material is in form of flakes.

The present invention regards production of thermal and acousticinsulation material.

The invention specifically regards a process for making cellulose-basedthermal and/or acoustic insulation material, for example by using papersludge. Such process is for example known from EP-A-0 429 735, howeverprovided wherein is the process of adding resins or other substances tothe sludge in order to confer mechanical characteristics to the endproduct. The German patent DE3307736 A1 describes a method forregenerating waste paper and cardboard in order to produce an aqueousmixture of fibres to be used as base material for producing thermal andacoustic insulations.

PRIOR ART

The processes known for production of cellulose thermoacousticinsulation material in form of flakes start from scrap paper, cardboardand waste paper. Due to long periods of storage, often outdoors or inhygienically unhealthy places, the raw material (scrap paper, cardboardand waste paper etc) may reach high levels of organic contamination thatconsist in the development of colonies of bacteria, insects, fungi etc.

Thus such raw material must be sanitised and protected against possiblenew procreation of microorganisms before being used. Observable amongproduction processes used currently are dry processes, whereinsanitisation occurs by adding bioinhibitors, such as for example boroncompounds (e.g. boric acid, borax, etc.) which are added dry.

Furthermore, the thermoacoustic insulation material obtained from suchprocesses has high contents of substances such as calcium carbonate,ink, glaze, etc., initially present on the scrap paper, cardboard andwaste paper, thus reducing the performance of the insulating material.

The wet process under patent DE3307736 A1 differs from those describedabove solely due to the fact that the initial material (scrap paper,cardboard and waste paper, etc) is moistened. In any case, the pulpobtained reveals the same defects due to the presence of unwantedsubstances which reduce the insulation performance, and still requires asanitizing process.

SUMMARY OF THE INVENTION

The present invention has the object of providing improved thermaland/or acoustic insulation material.

According to the present invention, such object is attained through thesolution specifically referred to in the claims that follow. The claimsform an integral part of the technical disclosure provided herein inrelation to the invention.

An embodiment of the present invention provides for the use of papersludge, preferably derived from industrial processes that use long fibrecellulose, to produce thermal and/or acoustic insulations in form offlakes. In particular, the present invention provides for the use wastepaper as secondary raw material, instead of first extraction celluloseor cellulose recycled in the known production cycles for manufacturingthermal and/or acoustic insulations, without requiring integrating thesame sludge with additives, substances or resins that confer mechanicalcharacteristics to the end material.

The invention allows reducing production of wastes in paper industries.Paper industry wastes are not contaminated biologically and thus do notrequire sanitising operations. Also the aspect of conserving durabilityis facilitated in that it is possible to intervene using a wider rangeof products such as for example fungicides, flame retardants, colouringagents, etc due to the possibility—provided for by the invention—ofusing additives both in solid phase and in liquid phase, allowingaddition of additives at several points of the process. Furthermore, thepaper industry wastes do not contain substances such as calciumcarbonate, glazing, ink which limit the thermal and acoustic insulationcapacity of the end product.

Other embodiments provide for the use of paper sludge, preferablyderiving from industrial processes that use “long fibre” cellulose,added to which are various substances and according to known techniquesin order to improve aspects different from the mechanical consistency ofthe end product, for example additivation with substances useful toimprove the durability of the product.

DETAILED DESCRIPTION

Now, the invention shall be described, strictly for exemplifying andnon-limiting purposes, with reference to the attached drawings, wherein:

FIG. 1 represents a first embodiment of a process for producing thermaland/or acoustic insulations in form of flakes;

FIG. 2 represents a second alternative embodiment of a process forproducing thermal and/or acoustic insulations in form of flakes.

Illustrated in the following description are various specific detailsaimed at providing an in-depth understanding of the embodiments. Theembodiments may be obtained without one or more specific details, orthrough other methods, components, materials etc. In other cases, knownstructures, materials or operations are not shown or described in detailto avoid obscuring aspects of the embodiments.

Reference to “an embodiment” in this description indicates that aparticular configuration, structure or characteristic describedregarding the embodiment is included in at least one embodiment. Hence,expressions such as “in an embodiment”, possibly present in variousparts of this description do not necessarily refer to the sameembodiment. Furthermore, particular configurations, structures orcharacteristics may be combined in any suitable manner in one or moreembodiments.

References herein are only used for facilitating the reader and thusthey do not define the scope of protection or the range of theembodiments.

The present description regards a process for producing cellulose-basedthermal and/or acoustic insulations using paper sludge and, inparticular, paper sludge mainly derived from processes that require longfibre cellulose as raw material.

The technical solution described herein provides for the use of papersludge for producing insulation material as direct surrogates for firstextraction cellulose or recycled cellulose or a combination of both.

The technical practicability of the invention lies in thecharacteristics of the sludge subject of the inventing suitable for suchpurpose.

The technical solution described herein may be summarised in the use ofwastes from known paper production industrial processes, for producingthermal and/or acoustic insulations in form of flakes.

Use of paper industry waste reduces the environmental impact of theproduct on the ecosystem, though there still remains impacts related tothe industrial production process. As a matter of fact a considerableshare of the paper industry environmental burden is represented by theproduction of paper sludge.

In this case, the environmental impact of paper sludge is so high thatthe national law provides that it be treated as “special waste”. Papersludge may also be classified as “polluting special waste” or“non-polluting special waste” depending on the chemical additives usedin the production process. In any case, costs incurred for disposing ofthese wastes are not negligible and they weigh, even considerably, onthe financial budgets of the paper industries.

Over the years, various technologies have been developed with the aim—onone hand—of reducing costs and—on the other hand—reducing theenvironmental impact of the paper industries.

Cellulose is a molecule capable of organising itself into chains andthus fibres. The mechanical characteristics of the paper produced arelinked to the length of the cellulose fibres. Cellulose may beclassified according to the mean length of the fibres. In literature,cellulose with fibres in the order of 20 microns is referred to as“short fibre”, cellulose with fibres in the order of 200 microns long isreferred to as “average fibre”, and cellulose having fibres in the orderof 1000 microns long is referred to as “long fibre”.

Conventional paper production methods (e.g. paper for photocopyingmachines) may employ a wide range of cellulose and in conventionalindustrial processes the residual material, i.e. sludge produced by thepaper industry, is purged by the cellulose fibres capable of conferringmechanical characteristics to the paper. Thus, conventional industrialprocesses produce paper sludge with none or extremely low mechanicalcharacteristics.

Known are methods for using such sludge. Currently, applicationsregarding reutilisation of sludge with relatively long fibre consists inproducing cardboard cores for rolls on which the same paper productionsshall be wrapped.

From an environmental point of view, the present invention reduces theamount of paper industry production wastes and has lower impact on theecosystem. Furthermore, paper industries gain a financial advantage inthat they have the possibility to convert waste material to be disposedof (i.e. a cost) into secondary raw material (i.e. a resource). Inaddition, availability of low cost raw material may help reducing theprice of the insulation material hence leading to an advantage for theusers too.

Paper sludge may be used as raw material in currently known conventionalindustrial processes for producing cellulose-based thermal and acousticinsulation material in form of flakes. Illustrated below forexemplification purpose, but solely regarding the description outlinedhereinafter, is a possible production process. The paper sludgeconsidered hereinafter may have different levels of water content.

EXAMPLE 1 Process for Producing Loose Insulation Material in Form ofFlakes

In the embodiment described herein, paper industry waste sludge withhigh amount of long, average and short fibre cellulose is used forproducing loose insulation material in form of flakes. A diagram of anindustrial process for producing the abovementioned loose insulationmaterial in form of flakes is illustrated in FIG. 1.

The industrial process A provides for that the paper industries 1produce particular papers 2 using average and long fibre cellulose. Thepaper sludge 3, derived from the industrial process A, is reutilized ina known industrial process B and used for producing thermal and/oracoustic insulations in form of flakes.

Regarding the process for producing insulation material in form offlakes B, the sludge 3 may be used as a surrogate or in combination withconventionally used raw material. The known industrial processes forproducing insulation material in form of flakes conventionally use firstextraction cellulose 11 and/or recycled cellulose 12 (scrap paper).

Thus, the industrial process B provides for initially subjectingsurrogate secondary raw material 3 (sludge) characterising the presentinvention optionally together with conventional raw material 11 and/or12 to a reduction of the size of the pieces by feeding them into acutting device 4. Subsequently, possibly a series of mixers 5 is usedfor homogenising material from different sources. The sludge 3 possiblyin first extraction cellulose 11 and/or recycled cellulose 12association is fed into a pulper 6. During processing in the pulper 6additives 7 (for example boron salts) useful to improve the durabilityof the end product 10, insulation material in form of flakes, may beadded. Sludge is thus introduced into a mill 8 possibly associated to adrying device 9. The mill 8 may contain metal percussion means (such asfor example balls or rolls) or other devices useable for the hammeringrequired to open the cellulose fibres, thus reducing density thereof andproducing flakes. The cellulose flake 10 obtained at the end of theprocess may be used for thermal and/or acoustic insulation.

Preferably, in order to improve the duration of insulation flakesfurther, fungicides are added to the sludge produced in the paperindustries. Even more preferably, such addition is performed in thepaper industries when sludge is still in flowable form, with a solidstate material content between 8% and 10% in weight. Alternatively,fungicides may be added during the aforeindicated process in the pulper6. Obviously, the construction details and embodiments may widely varywith respect to the details described and illustrated, without howeverdeparting from the scope of protection of the present invention, asdefined in the attached claims.

EXAMPLE 2 Process for Producing Loose Insulation Material in Form ofFlakes

In the embodiment described herein, paper industry wastes with highamount of long, average and short fibre cellulose are used for producingloose insulation material in form of flakes.

A diagram of an industrial process for producing the abovementionedloose insulation material in form of flakes is illustrated in FIG. 2.

The industrial process A provides for the production of special papers16 using virgin cellulose or recycled cellulose 12. After storage, thecellulose 13 reaches refining 14 where—on one hand—wastes of thesubsequent steps of the process 15 are supplied, while—on the otherhand—paper industry wastes which are stored and concentrated in the step17 are eliminated.

Should such wastes be intended to be used in a process for producinginsulation material in form of flakes of the type described above, itshould be preferably provided for that they be treated, while still inthe paper industry factory, with additives 18 in liquid solution. Suchadditives may be one or more from among flame retardants, fungicides,colouring agents, etc. It is also preferable that such additives beadded when the wastes or paper sludge are still in flowable form, withsolid state material content comprised between 8% and 10% in weight.

The wastes of the process A are thus subsequently dried in step 19, forexample mechanically by means of a screw feeder, and lastly, possiblytreated with additives 15 such as flame retardants, fungicides,colouring agents etc once again. In this further step, the additives maybe both in liquid form (solution) and solid form (powder).

The wastes thus produced may be transferred and used as raw material forthe process B of producing thermal and acoustic insulation material inform of flakes. Such wastes are substantially made up of sludge, havingsolid state material content comprised between 25% and 60% in weight.

The production process B illustrated in FIG. 2 represents an alternativeembodiment with respect to that illustrated in FIG. 1. Such processprovides for that the wastes of the process A be initially stored in astep 21 and possibly composed in a mixture that may also provide forfirst extraction cellulose 11 and/or recycled cellulose 12.

During storage, the wastes may be treated using additives 18 in liquidsolution (liquid phase) such as flame retardants, fungicides, colouringagents, etc.

The material is thus dried in a step 22, both naturally and by meansforced ventilation and/or heating systems, and subsequently moved tostep 23 for hammering 16. In such step, for example obtained by means ofa hammer mill, the dried material is expanded in volume until it formsinsulation flakes.

The flakes may also be treated with additives 15 in powder form, bothduring the hammering step and during the subsequent pre-packagingstorage 17.

1. Process for producing cellulose-based thermal and/or acousticinsulation material, characterised in that said insulation materialcomprises paper sludge and wherein said insulation material is in formof flakes.
 2. Process according to claim 1, wherein said paper sludgederives from processes that use long fibre cellulose.
 3. Processaccording to claim 1, wherein said insulation material is free ofbonding agents.
 4. Process is according to claim 1, wherein said papersludge is subjected to mechanical hammering operations.
 5. Process isaccording to claim 1, wherein said paper sludge does not comprisematerial made of sheet elements or the like.
 6. Process is according toclaim 1, wherein said paper sludge comprises a solid state materialcontent between 25% and 60% in weight.
 7. Process is according to claim1, wherein said paper sludge comprises a solid state material contentbetween 8% and 10% in weight.
 8. Process is according to claim 1,wherein at least one additive from among flame retardants, colouringagents and fungicides is added to the paper sludge.
 9. Process accordingto claim 8, wherein the additives are added in form of liquid solutionor powder material.
 10. Use of paper sludge for producing thermal and/oracoustic insulation material in form of flakes.
 11. Use according toclaim 10, wherein said paper sludge derives from processes using longfibre cellulose.
 12. Use according to claim 10, wherein said thermaland/or acoustic insulation material are produced through mechanicalhammering operations.